Mitogen stimulation of peripheral blood lymphocytes of duodenal ulcer patients during treatment with cimetidine or ranitidine.

During a double-blind randomised clinical trial of cimetidine and ranitidine in the management of duodenal ulcer, the response of patients' peripheral blood lymphocytes to optimal mitogenic stimulation in vitro has been measured. Treatment with cimetidine, but not ranitidine, was associated with a significant increase in the proportion of peripheral blood lymphocytes responding to this optimal mitogenic stimulation. We conclude that these effects of cimetidine may not be mediated at classical histamine H2-receptors.